Cite this article: Kanaya, Y., Matsui, H., Taketani, F., Pan, X., Komazaki, Y., Wang, Z., Chang, L., Kang, D., Choi, M., Kim, S.Y., Kang, C.H., Takami, A., Tanimoto, H., Ikeda, K. and Yamaji, K. (2017). Observed and Modeled Mass Concentrations of Organic Aerosols and PM2.5 at Three Remote Sites around the East China Sea: Roles of Chemical Aging.
Aerosol Air Qual. Res.
17: 3091-3105. https://doi.org/10.4209/aaqr.2016.12.0573
PM2.5 and its components were observed at three remote sites around the East China Sea.
With chemical aging, WRF-Chem model better reproduced the observed levels of organics.
High OH concentrations promoted secondary formation of organics with the VBS scheme.
Unaccounted sources of organic aerosols were implied besides the represented processes.
The model better reproduced the total PM2.5 levels when chemical aging was introduced.
Severe PM2.5 air pollution over the Asian continent is occasionally transported across the East China Sea by the westerly winds to Japan, continuing for long distances over the Pacific Ocean. Despite such polluted air masses causing health issues, conventional models tend to underestimate levels of organic aerosols (OA) and PM2.5. Here, PM2.5 and its major components recorded during three field campaigns carried out at Fukue Island (32.75°N, 128.68°E), Japan (spring 2009), Rudong (32.25°N, 121.37°E), China (spring 2010), and Jeju (33.35°N, 126.39°E), Korea (autumn 2012) around the East China Sea were used to test the performance of the Weather Research and Forecasting-Chem/ATRAS-MOSAIC model. Overall, model performance was improved by introducing chemical aging represented by a volatility basis-set scheme, whereby median values of the model/observation ratio for OA were raised to 0.34–1.28 from 0.30–0.35 in the case of conventional settings. In particular, the levels of OA at the Fukue site and daytime buildup of the OA levels at all three sites were reproduced by the model. OA levels were still sometimes underestimated. This suggests that either emission rates of organic precursors are being underestimated or other pathways of OA formation are also important. Our analysis also indicates that this region is characterized by high OH concentrations, promoting chemical aging. The predictions of PM2.5 levels in the model also improved, with median values of the model/observation ratio shifting from 0.67–0.91 to 0.68–0.95, when chemical aging of OA was taken into account.
Keywords: Chemical transport model; Regional-scale air pollution; Organics; Volatility basis-set scheme; Oxidative capacity